1. Field of the Invention
The present invention relates to object checking systems, particularly to a signature checking system, for instance, for certifying each card carrier by checking the hand-written signature entered to a signature checking terminal device with the reference data of the card carrier stored in a potable information memory.
2. Description of Related Art
There have been various object identification systems such as an image checking system using images of fingerprints, a voice checking system using voices such as voiceprints. Among them, a signature checking system using hand-written signatures of card carriers is considered useful because of its simple hardware structure, low manufacturing cost and less handling difficulty.
Such signature checking systems are used in various fields. For example, the signature checking system used for transactions (settlements) of credit cards etc. comprises, as shown in FIG. 10, a portable card type information memory 90 such as a credit card storing card-specific information including the card number, the card carrier's signature data used as the signature checking reference data, and the like; a signature checking terminal device 80 for identifying the carrier of the information memory 90 by checking the hand-written signature with the reference data stored in the information memory 90; and an external device (not illustrated) such as a host computer of a credit company or bank that settles the account according to the signature check result from the signature checking terminal device 80.
The signature checking terminal device 80 which is the core part of such a signature checking system is provided with e.g., an input panel 84 formed like a flat plate as shown in FIG. 10 so that the card carrier can sign on a slip or form 82 (receipt) placed on the panel 84. In the central part of the input panel 84 is built a tablet 86 used to read the signature written on the form 82. In addition, a clip 88 is attached to the top end of the input panel 84 and used to hold the form 82 tightly on the panel 84. The signature checking terminal device 80 is also formed so that the information memory 90 can be removed freely.
More specifically, as shown in FIG. 11, the signature checking terminal device 80 includes an information reader 92 for reading various data from the information memory 90; a signature checker 94 for checking the signature entered from the tablet 86 with the reference data read by the information reader 92 from the portable information memory 90; and a transaction determining unit 96 used to determine whether or not the card carrier who signed on the form is the right carrier of the information memory 90 and output the determination result to the external host computer, etc. The signature checker 94 and the settlement determining unit 96 are materialized usually by a microcomputer respectively.
In the prior art signature checking terminal device 80 formed such way, when the information memory 90 is loaded, the information reader 92 reads the signature from the information memory 90 and enters the data to the signature checker 94. When a signature is written on the form 82 put on the input panel 84 of the tablet 86 using a pen 83 that can sense and write signatures, the tablet 86 converts the position, writing pressure, and other data of the pen tip to coordinate data and writing pressure data. Those converted data are then entered into the signature checker 94.
The signature checker 94 then checks the signature with the reference data using a pattern matching method, for example, and the result is output to the transactions determining unit 96. In this case, how much both data items match can be represented by a value of how much the written signature is analogous to the reference data. More specifically, a space distance between the reference data and the newly entered data corresponding to a certain point of the reference value is measured, and the sum is evaluated as an evaluation function. The greater the space distance value is, the more the signature is determined nonanalogous from the registered signature. The smaller the value is, the more the signature is determined matching with the reference data. The signature checker 94 outputs the degree of matching to the settlement determining unit 96 as a value divided within 0.0 to 1.0.
The settlement determining unit 96 determines entered data (determination value) to be true when the value is 0.7 or over and to be false when the value is 0.3 or under. When the value is between 0.3 and 0.7, the signature input is requested again. If the signature is not entered again at this time, the signature check is determined to be canceled and the check itself is invalidated. The result (true or false) is then output to an external device such as the host computer. According to this output, the host computer or another settlement device executes necessary processing of transactions.
In this conventional signature checking system, however, since the information memory 90 and the signature checking terminal device 80 are manufactured according to a specific checking method (checking algorithm), those devices can correspond only to systems matching with the checking method of those devices.
That is, in the case of the signature checking system that checks each signature to certify the card carrier according to the reference data stored in the memory card, the system should preferably be able to use a plurality of types of information memories, each of which stores reference data provided by a different checking algorithm, in the same signature checking terminal device. However, in the conventional system, the information memory can be used only for specific signature checking terminal devices corresponding to the specific algorithm. Consequently, the system has such problems as a limited range of use and inconvenient incompatibility among terminal devices.